The fluorinated organophosphate nerve agents Tabun (GA), Sarin (GB), Soman (GD), and Cyclosarin (GF) are among the most toxic chemical warfare agents known. Together they comprise the G-series nerve agents, thus named because German scientists first synthesized them, beginning with GA in 1936. GB was discovered next in 1938, followed by GD in 1944 and finally the more obscure GF in 1949.
Sarin gas (O-Isopropyl methylphosphonofluoridate) and Soman gas O-Pinacolyl methylphosphonofluoridate), are colorless and odorless nerve gases, and since they are extremely volatile can spread quickly through the air.
Nerve gas attacks may come unexpectedly. It is important to be able to detect them at a high level of sensitivity because a gas cloud tends to disperse into low density portions and strands. It is also desirable to do so in a manner to communicate its detection quickly through an automated system and to enable detection over a distance.
The detection of nerve gases including Sarin and Soman at as early a time in the attack is critical to ameliorating or minimizing the consequences of the attack.
There are several methods for detecting Sarin and Soman which include spectroscopy methods and fluorescence methods.
Optical sensing technology for detecting the presence of an analyte includes a number of different types of sensors.
One such type of optical sensor is known as distributed intrinsic chemical optical fiber sensors such as those sold under the trademark DICAST by Intelligent Optical Systems, Inc. of Torrance Calif. The distributed intrinsic optical fiber sensors use the cladding of an optical fiber to contain a sensing chemical, an indicator chemical. In this type of sensor the optical fiber acts as both the sensing means and the transmission means for the signal and allows sensing over a considerable length of such distributed intrinsic optical fiber. Changes in the cladding caused by reaction of the sensing chemical change optical parameters of the light passing through the core of the fiber. Typically the change in the sensing chemical is a change in color and the change in the light is a change in absorption, which changes the intensity of the light that leaves the sensor. See for example U.S. Pat. Nos. 4,834,496 and 7,260,283 and 7,650,051 and 7,551,810 and 7,583,865 which are assigned to the assignee of this patent and the contents of which are incorporated herein by reference.
Another type of sensor called an “optrode” is a small body of material such as glass in which sensing chemistry is imbedded or on which sensing chemistry is coated. Optrodes are known as “point” sensors because they are small and can sense the presence of an analyte at only a particular point or a small area. An optrode sensing system may use optical fibers to carry a signal to and from the optrode. See for example U.S. Pat. Nos. 6,535,658 and 4,399,099 the contents of each of which are incorporated herein by reference.
More generally various types of waveguide configurations may be constructed with a sensing coating in which a parameter of the light passing through the waveguide will vary when the sensing coating is affected by an analyte that reacts with a sensing chemistry in the coating.